Re: [femm] Re: Incorrect force direction

["Greg Watson" <gowatson@xxxxxxxxxxxxxxxxx>]

----- Original Message -----
From: "Rob " <rtickle@xxxxxxxx>
To: <femm@xxxxxxxxxxx>
Sent: Thursday, January 04, 2001 4:35 PM
Subject: [femm] Re: Incorrect force direction


> I tend to agree with this, that is what my intuition says also, which
> is why this is an interesting problem. I think what the calculation
> might be saying is that the difference in reluctance between the 2
> sides becomes small enough to be down in the noise sooner than when
> your intuition might lead you to believe... I'm tempted to build this
> myself now and play around with it.

Hi Rob,

I wonder if part of the problem is not that David's FEMM assumes a 90 deg entry
angle for flux regardless of the permeability of the rails and the distance out
from the magnet. The right portion of the rails will be further up their B/H
curve than the left portion but if you look at the flux distribution contours
produced on the right & left sides of the magnet as the flux enters the rails
there is no difference to my eye.

FEMM seems to be producing a force to the left based on the same direction
fluxes from the return between the rails & that going from magnet pole to pole.
This would then produce a greater force to the left than to the right as
simulated.

Greg